X-Ray Fluorescence Yields of Al, Cl, Ar, Sc, Ti, V, Mn, Fe, Co, Y, and Ag

The $K$-fluorescence yields of elements in the range $13\le Z\le 27$ and the $L$-fluorescence yields of yttrium and silver have been measured. A monochromatic x-ray beam obtained through the Ross filter difference method produced the fluorescence in foil targets and argon gas, and some of the fluorescent x rays were detected by a flow counter mounted at right angles to the primary x rays. The incident x-ray flux was determined by a measurement in the same geometry of the x-ray flux scattered by helium. The fluorescence yields and standard deviations are ${\omega }_K\left(\mathrm{Al}\right)=0.0379\mathrm{}\pm 0.0023$, ${\omega }_K\left(\mathrm{Cl}\right)=0.0970\mathrm{}\pm 0.0054$, ${\omega }_K\left(\mathrm{Ar}\right)=0.119\mathrm{}\pm 0.007$, ${\omega }_K\left(\mathrm{Sc}\right)=0.190\mathrm{}\pm 0.010$, ${\omega }_K\left(\mathrm{Ti}\right)=0.221\mathrm{}\pm 0.012$, ${\omega }_K\left(\mathrm{V}\right)=0.250\mathrm{}\pm 0.012$, ${\omega }_K\left(\mathrm{Mn}\right)=0.303\mathrm{}\pm 0.017$, ${\omega }_K\left(\mathrm{Fe}\right)=0.347\mathrm{}\pm 0.022$, ${\omega }_K\left(\mathrm{Co}\right)=0.366\mathrm{}\pm 0.020$, ${\overline{\omega }}_L\left(\mathrm{Y}\right)=0.0315\mathrm{}\pm 0.0028$, and ${\overline{\omega }}_L\left(\mathrm{Ag}\right)=0.0659\mathrm{}\pm 0.0037$. The uncertainties include a 5% uncertainty in the helium-scattering cross section assumed for the data reduction. These $K$-fluorescence yields and the values for fluorescence yields for $Z\ge 30$ considered best by Fink, Jopson, Mark, and Swift are fitted with the semiempirical formula ${\left[\frac{{\omega }_K}{(1-{\omega }_K)}\right]}^n=A+BZ+C{Z}^3$, using $n=\frac{1}{4} \mathrm{and} \frac{1}{3}$. The best fit is given by ${\left[\frac{{\omega }_K}{(1-{\omega }_K)}\right]}^{\frac{1}{3}}=-0.1019+0.03377Z+1.178\mathrm{}\times {10}^{-6\mathrm{}}{Z}^3$, with a standard deviation of 2.4%.